Method of producing button-type batteries and spring-biased concave button-type battery

ABSTRACT

A button-type battery includes: a) an anode; b) a cathode positioned adjacent to the anode.; c) a separator and electrolyte between the anode and the cathode; d) a conductive first terminal housing member in electrical contact with one of the anode or the cathode, the first terminal housing member having a surrounding periphery and a concave central portion intermediate of its surrounding periphery; e) a conductive second terminal housing member in electrical contact with the other of the anode or the cathode, the second terminal housing member having a surrounding periphery and a concave central portion intermediate of its surrounding periphery which is opposingly concave to the concave central portion of the first terminal housing member; and f) the first and second terminal housing members being insulatingly joined and sealed at their respective peripheries to form an enclosed housing which retains and protects the anode, cathode, separator and electrolyte, with the concave central portions of the first and second terminal housing members projecting inwardly toward one another forming opposing inwardly sprung conductive terminals compressively forcing the anode, separator and cathode together. Methods of production are also disclosed.

TECHNICAL FIELD

This invention relates to button-type batteries.

BACKGROUND OF THE INVENTION

Button-type batteries are small thin energy cells that are commonly usedin watches and other electronic devices requiring a thin profile. Aconventional button-type battery includes an anode, a cathode, a porousseparator separating the anode and cathode, and an electrolyte withinthe separator pores.

These internal battery components are housed within a metal casing orhousing formed by a lower conductive can and an upper conductive lid.The can is typically in electrical contact with the cathode to form thepositive battery terminal, and the lid is in electrical contact with theanode to form the negative battery terminal. The can and lid are crimpedor pressed together to form a fluid-tight seal which entirely enclosesthe anode, cathode, separator, and electrolyte. An electricallyinsulating sealing gasket is provided within the primary seal betweenthe lid and can to electrically insulate the two housing members.

There is a need in button-type battery usage to make such energy cellsthinner. Today, the thinnest commercially available button-type batteryhas a thickness of 1.2 mm (47.2 mils). It would be desirable to make athinner battery, particularly one having a thickness of less than 1 mm(39.4 mils). A countering concern, however, is that the integrity of thefluid-tight seal cannot be compromised simply to achieve the goal ofthinner batteries.

It is also an objective in button-type battery design to create ahousing structure which physically compresses the anode, separator, andcathode together to insure proper operation of the energy cell. This istypically accomplished in the prior art by a separate internal springcomponent which provides desired compressive forces.

It would be desirable to design improved button-type batteries of verythin profile which meet at least one or more of the above statedobjectives.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below withreference to the following accompanying drawings. The same componentsand features illustrated throughout the drawings are referenced withlike numerals.

FIG. 1 is a side cross-sectional view of battery components constructedin accordance with the invention.

FIG. 2 is a side cross-sectional view of battery components constructedand arranged in accordance with the invention.

FIG. 3 is a side cross-sectional view of a button-type battery inaccordance with the invention.

FIG. 4 is an enlarged cross-sectional view of a peripheral sealingportion of the FIG. 3 button-type battery assembly.

FIG. 5 is a diagrammatic representation of pre-assembly andpost-assembly concavity of one component of a button-type battery inaccordance with the invention.

FIG. 6 is a diagrammatic representation of pre-assembled, mid-assemblyand post-assembly concavity of another component of a button-typebattery in accordance with the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of theconstitutional purposes of the U.S. Patent Laws "to promote the progressof science and useful arts" (Article 1, Section 8).

This invention concerns "coin" or "button-type" batteries. A button-typebattery is typically a small circular-shaped energy cell approximatelythe size of a coin. The button-type battery can be constructed indifferent sizes, with typical diameters being 12 mm, 16 mm, and 20 mm.Other shapes are possible, but the circular shape is most common.

In accordance with one aspect of the invention, a button-type batterycomprises:

an anode;

a cathode positioned adjacent to the anode;

a separator and electrolyte between the anode and the cathode;

a conductive first terminal housing member in electrical contact withone of the anode or the cathode, the first terminal housing memberhaving a surrounding periphery and a concave central portionintermediate of its surrounding periphery;

a conductive second terminal housing member in electrical contact withthe other of the anode or the cathode, the second terminal housingmember having a surrounding periphery and a concave central portionintermediate of its surrounding periphery which is opposingly concave tothe concave central portion of the first terminal housing member; and

the first and second terminal housing members being insulatingly joinedand sealed at their respective peripheries to form an enclosed housingwhich retains and protects the anode, cathode, separator andelectrolyte, with the concave central portions of the first and secondterminal housing members projecting inwardly toward one another formingopposing inwardly sprung conductive terminals compressively forcing theanode, separator and cathode together.

In accordance with another aspect of the invention, at least one of thecentral portions of the conductive first terminal housing member or thesecond terminal housing member is inwardly concave forming an inwardlysprung conductive terminal compressively forcing the anode, separatorand cathode together within the housing.

Research culminating in the invention disclosed herein also resulted inother inventions. These other inventions are the subject of other U.S.patents which spawned from patent applications filed on the same day ofthe patent application from which this U.S. patent matured. These otherpatent applications are U.S. patent application Ser. No. 08/205,590,"Methods Of Producing Button-Type Batteries And A Plurality Of BatteryTerminal Housing Members", listing Rickie Lake and Peter M. Blonsky asinventors. U.S. patent application Ser. No. 08/205,611, "Button-TypeBattery With Improved Separator And Gasket Construction", listing PeterM. Blonsky and Mark E. Tuttle as inventors and U.S. patent applicationSer. No. 08/205,957, "Button-Type Battery Having Bendable Construction,and Angled Button-Type Battery", listing Mark E. Tuttle and Peter M.Blonsky as inventors (now U.S. Pat. No. 5,432,027). These co-filedpatent applications and resulting patents are hereby incorporated byreference as if fully included herein.

Referring to the drawings, FIG. 1 illustrates a conductive firstterminal housing member 10 and a conductive second terminal housingmember 12. First terminal housing member 10 includes a surroundingperiphery 14, while second housing member 12 includes a surroundingperiphery 16. Surrounding periphery 14 is defined by a peripheral bend60° of 90° or less which produces outwardly projection portions 62, andthereby defines a container-like construction. First terminal member 10also has a pre-formed concave central portion 18 intermediate itssurrounding periphery 14 which extends inwardly from its outer surface.

Second terminal housing member 12 comprises a lid for first terminalhousing member 12, and has a concave central portion 20 intermediate itssurrounding periphery 16 which also extends inwardly from its outersurface. Accordingly, at least one of the central portions of thehousing members is concave, with a preference being that both areconcave. Housing members 10 and 12 are arranged such that theirconcavities inwardly oppose one another. For purposes of the continuingdiscussion, original concavity of central portion 18 is to a firstdegree, while original concavity of central portion 20 is to a fourthdegree. Preferably, the first and fourth degrees of concavity are thesame. Specifically, each concavity is preferably substantially arcuatein shape, having a radius of curvature less than or equal to about 400mm, with less than or equal to 200 mm being most preferred.

First terminal housing member 10 and second terminal housing member 12are each preferably formed from a metal sheet having a thickness lessthan about 8 mils, and preferably in a range of from about 3 mils to 5mils. An example material includes Type 304 stainless steel having 4mils thickness.

First terminal member 10 and second terminal member 12 are aligned alonga common central axis 22. Second terminal housing member 12 includes anannular planar periphery portion 24 effectively projecting substantiallyradially outward relative to the central axis 22. For purposes of thecontinuing discussion, periphery portion 24 includes three sides 50, 51and 52. First terminal housing member 10 includes and annular adheredgasket material 26. Such is preferably provided in a manner described inour U.S. patent application Ser. No. 08/205,590, entitled "Methods OfProducing Button-Type Batteries And A Plurality Of Battery TerminalHousing Members", listing Rickie Lake and Peter M. Blonsky as inventors.In forming first terminal housing member 10 with adhered gasket material26, the cutting and forming step of our "Methods Of ProducingButton-Type Batteries And A Plurality Of Battery Terminal HousingMembers" patent would most preferably be provided with a lower convexlydomed portion to produce central concave portion 18.

Referring to FIG. 2, an anode 28, separator 30 and cathode 32 arepositioned within first terminal housing member (container) 10. Liquidelectrolyte 34 is also provided within housing 10. Anode 28 will be inelectrical contact with concave central portion 20 of the secondterminal housing member 12, while cathode 32 will be in electricalcontact with concave central portion 18 of first terminal housing member10. Anode 28, separator 30 and cathode 32 are centrally aligned alongtransverse central axis 22.

Cathode 32 is formed of a compressed tablet made from a combination ofmanganese (IV) oxide, carbon, and teflon powder. An example preferredthickness of cathode 33 is 8 mils (0.2032 mm). Separator 30 is a wovenor porous polymeric material, such as polyethylene, polypropylene, orteflon. An example preferred thickness of separator 30 is 1 mil (0.0254mm). Anode 28 is formed of elemental lithium provided on a copper backedfoil. An example thickness of anode 28 is 2 mils (0.0508 mm).

An example electrolyte 34 comprises a solution of propylene carbonateand ethylene glycol dimethylether, having dissolved lithiumtetrafluoroborate. Suitable electrolyte components are supplied byAldrich Chemical Company of Milwaukee, Wis. The volume of electrolyte 34provided within first terminal housing member 10 is preferably gauged tofill the substantial void within housing member 10, yet not so great toleak out upon crimp sealing the battery assembly.

Referring to FIG. 3, first and second terminal housing members 10 and 12are insulatingly joined and sealed at their respective peripheries toform an enclosed housing which retains and protects the anode cathodeseparator and electrolyte. The preferred manner of joining and sealingthe battery is as described in our "Methods Of Producing Button-TypeBatteries And A Plurality Of Battery Terminal Housing Members" patent.The joining results in the first terminal housing member peripherywrapping around the three sides of the second terminal housing memberperiphery.

Specifically, second housing member 12 is pressed downwardly somewhatwhile peripheral portions 62 of first terminal housing member 10 arefurther bent inwardly from 90° about peripheral bend 60. In thepreferred embodiment, the initial bend past 90° is by an additional 30°.This partial crimp effectively, if only temporarily, holds secondterminal housing member 12 in a desired position with anode 28,separator 30 and cathode 32 therebeneath. Further, this initial bendpast 90° is understood to temporarily impart additional or increasedarcuate concavity to circular central base portion 18 in the illustratedupward direction to a second degree from flatness. This results from acombination of the thickness of the central portion and the radius ofbend 60 being in combination effectively small or diminutive that theresultant compressive stresses cause such upward contraction. An exampleradius of curvature in accordance with the above described preferredembodiment is 3.5 mils (0.0889 mm). The additional concave bending isbelieved to be temporary because continued bending of the peripheralportions of a flat-bottom, empty first terminal housing member resultsin flattening of the arc and overall less indentation.

From the pre-crimp stage, sealing peripheral portions 62 of firstterminal housing member 10 are further bent about peripheral bend 60 toform a single continuous peripheral bend which effectively crimps firstand second terminal housing members 10 and 12 together. Such effectivelyforms an enclosed battery housing with gasket material and separatormaterial being interposed between the first and second terminal housingmembers to provide a fluid-tight seal and to provide electricalinsulation therebetween. A battery made in accordance with the aboveexample thickness components will have a finished total thickness of 0.5mm (19.7 mils).

One known prior art button-type battery (no available literature) isknown to utilize a bottom can having an indented central bottom surface.However, the indented surface is not understood to impart any inwardcompressive spring force to the internal components. Accordingly, thisprior art button-type battery is believed to be no more pertinent thanthat disclosed in U.S. Pat. No. 2,422,045.

Referring with more specificity to the drawings, the joined firstterminal housing member 10 (FIG. 3) comprises a peripheral portion 36having two substantially planar and parallel opposing segments 38 and40. First terminal housing member peripheral portion 36 further includesa continuously bending segment 42 interconnecting the substantiallyplanar and parallel segments 38 and 40. Such a construction effectivelywraps around the three sides 50, 51 and 52 of second terminal housingmember periphery 24. In the illustrated and preferred embodiment, secondterminal housing periphery 24 and segments 38 and 40 are allsubstantially parallel.

The concave central portions of first and second terminal housingmembers 10 and 12 project inwardly toward one another forming opposinginwardly sprung conductive terminals which compressively force the anodeseparator and cathode together. Such is accomplishable in very thinbatteries, such as less than 1 mm or even less then 0.5 mm, to provide abattery void of any :internal spring component but for the opposingconcavity of the first and second terminal housing members.

The concave indentations of original central portions 18 and 20 willdiminish in degree, even to the point of indented flatness or planarity,upon final engagement and crimping as illustrated in FIG. 3. Theseportions are correspondingly designated with numerals 18a and 20a. Theoriginal pre-formed concavity still, however, provides the inwardresilient spring force which compressively holds the internal componentsof the battery together in tight juxtaposition.

Such is further diagrammatically shown and described with reference toFIGS. 5 and 6. The upper line of FIG. 5 diagrammatically illustrates thepreferred embodiment central portion of second terminal housing member12 being downwardly concave to the stated starting fourth degree ofconcavity, designated "A". The lower line of FIG. 5 diagrammaticallyillustrates the resultant or assembled concavity to the fifth degree,designated "B", which is less than the fourth degree.

The upper line of FIG. 6 diagrammatically illustrates the statedstarting first degree of concavity. Such is designated with the letter"A" as in the preferred embodiment the central starting concavities offirst housing member 10 and second housing member 12 are the same. Themiddle line of FIG. 6 represents the stated second degree of concavity,designated "C", which is greater than first concavity "A". The bottomline represents the assembled stated third degree of concavity,designated "D", which is less than "A" but greater than "B".

Property rights are also asserted in methods of forming button-typebatteries, as evidenced by the concluding claims.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

We claim:
 1. A button-type battery comprising:an anode; a cathodepositioned adjacent to the anode; a separator and electrolyte betweenthe anode and the cathode; a conductive first terminal housing member inelectrical contact with one of the anode or the cathode, the firstterminal housing member having a surrounding periphery and a concavecentral portion intermediate of its surrounding periphery; a conductivesecond terminal housing member in electrical contact with the other ofthe anode or the cathode, the second terminal housing member having asurrounding periphery and a concave central portion intermediate of itssurrounding periphery which is opposingly concave to the concave centralportion of the first terminal housing member; and the first and secondterminal housing members being insulatingly joined and sealed at theirrespective peripheries to form an enclosed housing which retains andprotects; the anode, cathode, separator and electrolyte, with theconcave central portions of the first and second terminal housingmembers projecting inwardly toward one another forming opposing inwardlysprung conductive terminals compressively forcing the anode, separatorand cathode together.
 2. A button-type battery according to 1 whereinthe concave central portions at least prior to joining are arcuatelyshaped.
 3. A button-type battery according to 1 wherein the concavecentral portions at least prior to joining are arcuately shaped, witheach having some radius of curvature, less than or equal to about 400millimeters.
 4. A button-type battery according to 1 wherein thebutton-type battery is void of any internal spring component but for theopposing concavity of the first and second terminal housing members. 5.A button-type battery according to 1 wherein the first and secondterminal housing members are formed of metal sheets having thicknessesof less than 8 mils.
 6. A button-type battery according to claim 1wherein a total combined thickness of the anode, the cathode, theseparator, and the first and second terminal housing members is lessthan 1 millimeter.
 7. A button-type battery according to claim 1 whereina total combined thickness of the anode, the cathode, the separator, andthe first and second terminal housing members is approximately 0.5millimeter or less.
 8. A button-type battery according to claim 1wherein a total combined thickness of the anode, the cathode, theseparator, and the first and second terminal housing members is lessthan 1 millimeter; and being void of any internal spring component butfor the opposing concavity of the first and second terminal housingmembers.
 9. A button-type battery according to claim 1 wherein a totalcombined thickness of the anode, the cathode, the separator, and thefirst and second terminal housing members is approximately 0.5millimeter or less; and being void of any internal spring component butfor the opposing concavity of the first and second terminal housingmembers.
 10. A button-type battery according to 1 wherein the first andsecond terminal housing members are formed of metal sheets havingthicknesses in a range from about 3 mils to 5 mils, with the batterybeing void of any internal spring component but for the opposingconcavity of the first and second terminal housing members.
 11. Abutton-type battery according to 1 wherein,the concave central portionsat least prior to joining are arcuately shaped, with each having someradius of curvature less than or equal to about 400 millimeters; and thefirst and second terminal housing members are formed of metal sheetshaving thicknesses of less than 8 mils, with the battery being void ofany internal spring component but for the opposing concavity of thefirst and second terminal housing members.
 12. A button-type batteryaccording to 1 wherein,the concave central portions at least prior tojoining are arcuately shaped, with each having some radius of curvatureless than or equal to about 400 millimeters; and the first and secondterminal housing members are formed of metal sheets having thicknessesin a range from about 3 mils to 5 mils, with the battery being void ofany internal spring component but for the opposing concavity of thefirst and second terminal housing members.
 13. A button-type batteryaccording to claim 1 wherein:the anode and cathode are aligned along atransverse central axis; the second terminal housing member periphery isplanar and projects substantially radially outward from the centralaxis; the first terminal housing member periphery wraps around threesides of the second terminal housing member periphery, the firstterminal housing member periphery having two substantially planarsegments on opposing sides of the second terminal housing memberperiphery and a continuously bending segment on a third side of thesecond terminal housing member periphery connecting the twosubstantially planar segments.
 14. A button-type battery according toclaim 13 wherein the planar second terminal housing member periphery andthe two substantially planar segments of the first terminal housingmember periphery are all substantially in parallel.
 15. A button-typebattery according to 13 wherein the concave central portions at leastprior to joining are arcuately shaped.
 16. A button-type batteryaccording to 13 wherein the concave central portions at least prior tojoining are arcuately shaped, with each having some radius of curvatureless than or equal to about 400 millimeters.
 17. A button-type batteryaccording to 13 wherein the button-type battery is void of any internalspring component but for the opposing concavity of the first and secondterminal housing members.
 18. A button-type battery according to 13wherein the first and second terminal housing members are formed ofmetal sheets having thicknesses of less than 8 mils.
 19. A button-typebattery according to claim 13 wherein a total combined thickness of theanode, the cathode, the separator, and the first and second terminalhousing members is less than 1 millimeter.
 20. A button-type batteryaccording to claim 13 wherein a total combined thickness of the anode,the cathode, the separator, and the first and second terminal housingmembers is approximately 0.5 millimeter or less.
 21. A button-typebattery according to claim 13 wherein a total combined thickness of theanode, the cathode, the separator, and the first and second terminalhousing members is less than 1 millimeter; and being void of anyinternal spring component but for the opposing concavity of the firstand second terminal housing members.
 22. A button-type battery accordingto claim 13 wherein a total combined thickness of the anode, thecathode, the separator, and the first and second terminal housingmembers is approximately 0.5 millimeter or less; and being void of anyinternal spring component but for the opposing concavity of the firstand second terminal housing members.
 23. A button-type battery accordingto 13 wherein the first and second terminal housing members are formedof metal sheets having thicknesses in a range from about 3 mils to 5mils, with the battery being void of any internal spring component butfor the opposing concavity of the first and second terminal housingmembers.
 24. A button-type battery according to 13 wherein,the concavecentral portions at least prior to joining are arcuately shaped, witheach having some radius of curvature less than or equal to about 400millimeters; and the first and second terminal housing members areformed of metal sheets having thicknesses of less than 8 mils, with thebattery being void of any internal spring component but for the opposingconcavity of the first and second terminal housing members.
 25. Abutton-type battery according to 13 wherein,the concave central portionsat least prior to joining are arcuately shaped, with each having someradius of curvature less than or equal to about 400 millimeters; and thefirst and second terminal housing members are formed of metal sheetshaving thicknesses in a range from about 3 mils to 5 mils, with thebattery being void of any internal spring component but for the opposingconcavity of the first and second terminal housing members.
 26. Abutton-type battery comprising:an anode; a cathode positioned adjacentto the anode; a separator and electrolyte between the anode and thecathode; a conductive first terminal housing member in electricalcontact with the cathode, the first terminal housing member having asurrounding periphery and a central portion intermediate of itssurrounding periphery; a conductive second terminal housing member inelectrical contact with the anode, the second terminal housing memberhaving a surrounding periphery and a central portion intermediate of itssurrounding periphery; and the first and second terminal housing membersbeing insultingly joined and sealed at their respective peripheries toform an enclosed housing which retains and protects the anode, cathode,separator and electrolyte; the central portion of the conductive firstterminal housing member being inwardly concave forming an inwardlysprung conductive terminal compressively forcing the anode, separatorand cathode together within the housing.
 27. A method of forming abutton-type battery comprising the following steps:providing aconductive first terminal housing member having a surrounding peripheryand a central portion intermediate its surrounding periphery; the firstterminal housing member forming a container within which is received ananode, a cathode positioned adjacent to the anode, and a separator andelectrolyte between the anode and the cathode; the first terminalhousing member central portion being in electrical contact with one ofthe anode or the cathode; providing a conductive second terminal housingmember having a surrounding periphery and a central portion intermediateits surrounding periphery, the second terminal member forming a lid forthe first terminal housing member container, the second terminal housingmember central portion having an outer surface and being concave to afirst degree from its outer surface in the direction of the firstterminal housing member container; positioning the second terminalhousing member lid and the first terminal housing member container withthe anode, the cathode, separator and electrolyte therewithin in sealingjuxtaposition to one another; and insulatingly joining and sealing thesecond terminal housing member juxtaposed lid and the first terminalhousing member container at their respective peripheries to form anenclosed housing which retains and protects the anode, cathode,separator and electrolyte; the other of the anode or the cathode beingin electrical contact with the second terminal housing member centralportion; the concave central portion of the joined second terminalhousing member applying an inward spring force compressively forcing theanode, separator and cathode together during a combination of thepositioning and joining and sealing steps; the concave central portionof the joined second terminal housing member being concave to a seconddegree from its outer surface in the direction of the first terminalmember container, the second degree being less than the first degree.28. The method of forming a button-type battery of claim 27 wherein thefirst degree concavity is less than or equal to about 400 millimeters.29. A method of forming a button-type battery comprising the followingsteps:providing a conductive first terminal housing member having asurrounding periphery and a central portion intermediate its surroundingperiphery; the surrounding periphery including a peripheral bend of 90°or less producing outwardly projecting portions which define acontainer; an anode, a cathode positioned adjacent to the anode, and aseparator and electrolyte between the anode and the cathode beingprovided within the container; the first terminal housing member centralportion being in electrical contact with one of the anode or thecathode; the first terminal housing member central portion having anouter surface and being concave to a first degree from its outer surfacein the direction of the first terminal housing member projectingportions; providing a conductive second terminal housing member having asurrounding periphery and a central portion intermediate its surroundingperiphery, the second terminal member forming a lid for the firstterminal housing member container; positioning the second terminalhousing member lid and the first terminal housing member container withthe anode, the cathode, separator and electrolyte therewithin in sealingjuxtaposition to one another; and with the second terminal housingmember lid and the first terminal housing member container being insealing juxtaposition, bending the first terminal housing memberprojecting portions about the peripheral bend beyond 90°, the firstterminal housing member being formed of a sheet having a thickness, thefirst sheet thickness and peripheral bend radius in combination beingeffectively diminutive to increase concavity of the first terminalmember central portion to a second degree as a direct result of suchbending; further bending the first terminal housing member projectingportions about the peripheral bend to seal the lid and containertogether at their peripheries into a sealed battery enclosure; the otherof the anode or the cathode being in electrical contact with the secondterminal housing member central portion; the concave central portion ofthe joined first terminal housing member applying an inward spring forcecompressively forcing the anode, separator and cathode together during acombination of the positioning, bending and further bending steps; theconcave central portion of the joined first terminal housing memberbeing concave to a third degree from its outer surface in the directionof the second terminal member container, the third degree being lessthan each of the first and second degrees.
 30. The method of forming abutton-type battery of claim 29 wherein the first degree concavity isless than or equal to about 400 millimeters.
 31. The method of forming abutton-type battery of claim 29 wherein the second terminal housingmember is provided with a central portion which is concave in a fourthdegree from its outer surface in the direction of the first terminalhousing member container prior to the steps of positioning, bending andfurther bending; the concave central portion of the joined secondterminal housing member applying an inward spring force compressivelyforcing the anode, separator and cathode together during a combinationof the positioning, bending and further bending steps; the concavecentral portion of the joined second terminal housing member beingconcave to a fifth degree from its outer surface in the direction of thefirst terminal member container, the fifth degree being less than eachof the first and second degrees.
 32. The method of forming a button-typebattery of claim 29 wherein the first and fourth degree concavities areindividually less than or equal to about 400 millimeters.